Rangeley Formation, undivided (NHSr;0)

State	New Hampshire
Name	Rangeley Formation, undivided
Geologic age	Lower Silurian (Llandoverian)
Original map label	Sr
Comments	Part of the Central Maine Composite Terrane (Central Maine Trough) - Variably metamorphosed sedimentary and volcanic rocks of greenschist to granulite facies, locally migmatized. Area includes structural belts between the Monroe fault on the west and the Campbell Hill fault on the east; that is, the Bronson Hill anticlinorium, Piedmont allochthon, Kearsarge-central Maine synclinorium, central New Hampshire anticlinorium, and Rochester-Lebanon (Maine) antiformal synclinorium. Secondary unit description from USGS Geologic Names lexicon (ref. NH047): Mapped undivided and as eight subdivisions. Subdivisions include ribbon-banded calc-silicate of eastern NH (probable equivalent of Patch Mountain Member of Sangerville Formation of central ME); unnamed lower part of Rangeley, which consists of gray, thinly laminated metapelite with local lentils of turbidites and thin quartz conglomerates in western NH and sparse calc-silicate pods and coticule (probable equivalent of member B of Rangeley in ME); basaltic metavolcanics in Dixville region in Piermont allochthon; felsic metavolcanics in Dixville region in Piermont allochthon; schist matrix conglomerate within gray uppermost part of Rangeley in southwestern NH; pink to green, thinly bedded calc-silicate and purple biotite granofels close to transition from lower to upper parts of Rangeley; member C of Rangeley in northeastern NH and ME, consisting of quartz-pebble conglomerate overlain by rusty metapelite and feldspathic quartzite; and an unnamed upper part consisting of rusty-weathering pelitic schist, metasandstone, and local grits with common calc-silicate pods and minor coticule (probable equivalent of member C of Rangeley in ME). Unnamed calcsilicate and granofels unit is traced into Paxton Formation in north-central MA, where it was mapped as a "western belt" of Paxton and Littleton Formations on MA State Geologic Map by Zen and others (1983); rocks previously assigned to Paxton and Littleton Formations are now reassigned to Rangeley Formation in MA on the basis of more recent mapping (Robinson and Goldsmith, 1991). Aleinikoff and Moench (1987) determined an isotopic age of 432 +/-8 Ma using U/Pb methods on felsic metatuff from Rangeley.
Primary rock type	metasedimentary rock
Secondary rock type	calc-silicate rock
Other rock types	meta-argillite; quartzite; pelitic schist; granofels; felsic metavolcanic rock
Lithologic constituents	Major Metamorphic > Metasedimentarymetapelite, metasandstone, and local coarse-grained metasandstone lentils Minor Metamorphic > Metaigneous > Metavolcanicfelsic metavolcanic rocks Metamorphic > Granoblastic > Granofelsbiotite granofels Metamorphic > Metasedimentary > Metaclastic > Pelitic-schistpelitic schist Metamorphic > Metasedimentary > Calc-silicate-rockribbon-banded calc-silicate, calc-silicate pods Sedimentary > Clastic > Conglomeratequartz-pebble conglomerate Metamorphic > Metasedimentary > Metaclastic > Quartzitefeldspathic quartzite
Map references	Bennett, D. S, , Wittkop, C.A., and Dicken, C.L., 2006 , Bedrock Geologic Map of New Hampshire - A Digital Representation of the Lyons and others 1997 map and ancillary files: U.S. Geological Survey Data Series 215, scale 1:250,000, CD-ROM. [http://pubs.er.usgs.gov/publication/ds215]
Unit references	Lyons, J.B., Bothner, W.A., Moench, R.H., and Thompson, J.B., Jr., 1997, Bedrock Geologic Map of New Hampshire: Reston, VA, U.S. Geological Survey Special Map, 1:250,000, 2 sheets. USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/]
Geographic coverage	Carroll - Coos - Grafton - Hillsborough